Injector for internal combustion engines



Filed Dec. 23, 1958 2 Sheets-Sheet 1 May 20, 1941. P. LORANGE I INJECTORFOR INTERNAL COMBUSTION ENGINES Filed Dec. 23, 1958 2 Sheets-Sheet 2Patented May 20, 1941 INjE-CTOR ron INTERNAL COMBUSTION ENGINES ProsperLOrange, Stuttgart-Feuerbach, Germany; Rudolf LOrange executor of theestate of said Prosper LOrange, deceased Application December 23, 1938,Serial No. 247,528 In Germany June 24, 1938 9 Claims. (Cl. 299-1075) Theinvention relates to injectors for-internal combustion engines, and inparticular to injectors of the needle-valve type.

Such injectors are opened by the pressure of the fuel acting on the tipof the spring-loaded valve needle above the seating thereof, the spaceabove the upper or other end of the needle not being subjected to fuelunder pressure. As oil always leaks to the space above the needle, it isnecessary to provide a pipe for the withdrawal of oil from this space.

The spring by which the needle is forced upon its seat must be so strongthat it is not compressed until a certain opening pressure, which issometimes very high, has been attained. When the pump pressure ceases,the pressure exerted by the spring forces the needle on to its seat,which is of relatively small area.

Many designs of injectors have been proposed to cause the production ofa small preliminary injection as early as possibl before the mainimection.

The chief object of the invention is to furnish an injector in whichfuel under pressur is present above the end of the needle remote fromthe nozzle, whereby the provision of a conduit for the removal ofescaped oil is obviated.

Another object of the invention is to provide an injector in which asubstantially weaker loading spring for the needle than that normallyemployed can be utilised, whereby the hammering action of the needle onits seat and the resulting wear are diminished.

A,. further object of the invention is the provision of an injector inwhich a preliminary fuel injection is efiected in a particularlyadvantagBO'llS manner.

The above and further objects of the invention will now be describedwith reference to the annexed drawings, in which Figure 1 represents apressure diagram;

Figure 2 illustrates an axial section of an injector with an invariablethrottling aperture;

Figure 3 is a similar view of an injector the throttling aperture ofwhich is controlled by a valve; and

Figure 4 illustrates a further embodiment of the type of injectorillustrated in Figure 3.

In the injector according to the invention the space above the end ofthe needle remote from the nozzle communicates with the fuel deliverypipe by means of only one or more apertures having a strong throttlingaction and with the combustion chamber through a fine calibre injectionaperture, the needle being pressed on its valve seat by means of aspring, whereby'when fuel is forced-through the delivery pipe from thepump, the pressure set up in the said space becomes so much smaller thanthe pressure at the tip of the needle above the valve seat, that theforce of the spring is overcome and the needle rises from its seat.

The needle is preferably axially bored for the flow of fuel therethroughto the injection aperture.

The injector may operate in the following. manner:

As soon as the pump pressure is set up in the delivery pipe, fuel flowsthrough the throttling aperture or apertures into the space above theneedle and then through the' axially bored needle and the fine calibreinjection aperture at the tip thereof into the combustion chamber. Theinjection aperture is so dimensioned that only a fraction, for exampleone sixth, of the entire fuel charge is injected therethrough.

A drop in pressure of the fuel flowing through the throttling apertureor apertures and the injection aperture occurs. The pressure decreasesat the injection aperture opening into the combustion chamber to thelevel of the counterpressure in the said combustion chamber, the fuelunder pressure being sprayed into the cylinder.

At the throttling aperture or apertures between the delivery pipe andthe space above the needle, the pressure drop can be so controlled byselection of the ratio of the throttling aperture to the injectionaperture in the tip of the needle, that it amounts to a predeterminedfraction of the pump pressure, for example to approximately 20atmospheres in the case of a pump pressure of about atmospheres. Theratio of the pressures at a given instant will thus be approximatelythat indicated in the pressure diagram constituting Figure 1 of theaccompanying drawings. The full pump pressure, or the pump pressure P1reduced by the throttling in the delivery pipe obtains up to thethrottling aperture or apertures between the said delivery pipe and thespace above the needle.

After the fuel has passed throughthe throttling aperture it is reducedto a pressure P2, so that from this throttling aperture to the injectionaperture at the tip of the needle the pressure P2 obtains, which thenfalls through the injection aperture to a pressure P3, which issubstantially equal to the pressure in the combustion chamber.

As soon as the pressure difference P1-P2 has become so great that thespring load on the needle is less than the vertical component of thesuper-pressure exerted on the needle above the valve seat at'the tipthereof, the needle rises,

. the said needle closing again when the pressure in the pressureannular space surrounding the needle tip decreases. 'For a short timebefore the needle opens, only the jet from the injection aperture in thtip of the needle is sprayed into the combustion chamber and thus thedesired preliminary injectionisattained. 7

When the needle closes, the pressure in the space above the needle willin any case decrease more rapidly than the pump pressure, since theneedle, forced down by its spring, exerts a sucking action. Thisarrangement aifords the following advantages:

1. In contra-distinction to normal constructions, the danger ofcarbonisation at the nozzle due to a preliminary injection (preliminarydripping) does not occur, since any drips escaping before the maininjection are carried away by the full jet later sprayed past from theneedle nozzle, whilst the eflect 'of subsequent dripping is eliminatedowing to the fact that the pressure falls more rapidly in the spaceabove the needle than in the delivery pipe, and the spray through theinjection aperture at the tip of the needle therefore ceases ,morerapidly than the spray through the nozzle.

2. As compared with the normal needle-valve type injector'the advantageis obtainedthat the conduit for the removal of escaped fuel isobviated.- The fuel penetrating past the needle is simply added to fuelentering through the throttling aperture.

3. The loading spring for the needle can be made very considerablysmaller and weaker, for example one eighth as strong as the springusually employed. In this manner, the heavy hammering of the needle onto its very narrow seat and the wear-thus produced are diminished.

4. The fuel is sprayed through the fine aperture in the tip of theneedle somewhat earlier than the injection through the nozzle, and thepreliminary ignition, which is generally very desirable, is thusefiected and shortens th usual delay in ignition.

5. In the case of an engine furnished with a pre-combustion chamberwhich has a conduit disposed opposite the injection nozzle extending tothe main combustion chamber, it is possible to make the fine jet sprayedfrom the aperture in the tip of the needle penetrate through into themain chamber owing to the fact that it is particularly well guided, forexample the length of the fine aperture may be four times greater thanits diameter. This will be particularly advantageous for initiating theignition if the air velocity in the conduit is not so high at thestarting speed that the jet is blown back.

The pressure diiference P1Pa will vary with the fuel velocity in thedelivery pipe, that is to say with the engine speed, and it may bedesirable that this value, and consequently the needle opening pressure,should be. maintained constant.

This may be effected without difliculty if the throttling aperture isclosed by a spring-leaded The difference in the manner of operation whena throttling aperture of invariable cross-section or one provided with aspring-loaded throttle valve is employed is as follows:

The needle opening pressure is reached more rapidly in the former casewhen the speed is higher. When the needle closes in the former case, theentire pressure will be removed from the delivery pipe, provided thatthis pipe is not closed by a non-return valve, whilst in the second casea pressure of the value of the differential pressure determined by thethrottle valve remains in the delivery pipe,

In Figure 2, the casing A, which is pressed on to its seat by thescrewthreadednut member B, contains the guide C for the nozzle needlevalve F and the nozzle plate E. Both the guide C and the nozzle plate Eare pressed on to the lower edge of the casing A by the screw cap D.

The guide C contains the ground-in and axially bored needle F, which isloaded by the spring G. v

The spring G bears against the apertured cover H screwed into the topend of the guide 0, the aperture of the plug H terminating in the finecalibre throttle aperture J, whilst the bore of the needle F extendingtowards the tip thereof terminates in the fine calibre injectionaperture K.

delivery pipe, fuel flows through the-throttle aperture J into the spaceabove the needle F and then traverses the bore in the needle F, and isinjected through the fine aperture K into the combustion chamber.

The annular space at the tip of the needle F receives the full pumppressure, whilst the space above the said needle Fis subject to a lowerpressure determined by the size of the apertures J and K.

The resultant pressure of the pressures in the spaces above and belowthe needle F acts in the direction of opening of the needle F andeventually attains a value greater than the pressure exerted on theneedle F by the spring G. The

needle F then rises, either to its limit or until equilibrium with theloading spring pressure is established.

The mainfuel injection, into the combustion chamber now occurs, eitherin the form of a solid or hollow jet of fuel, the additionaljet sprayedfrom the aperture K being maintained as in each case.

If the pressure of the pump decreases, the pressure difference betweenthe spaces above and below the needle F is also lowered, and at acertain pressure value the spring G is strong enough to return theneedle F to its seat. If in this case the pressure drop in the deliverypipe is accelerated by a load-relieving device, there will not be apressure in the delivery pipe when the needle F returns to its seat andfurther fuel will not be injected, since the pressure above the needle Fmust, in accordance with the spring pressure, always be less than thepressure in the delivery pipe.

Figure 3 illustrates a construction suitable for use with the usualneedle-valve type injector.-

The casing A comprises the screwthreaded head B, which also carries theconical seating for the end of the delivery pipe.

the core The casing A contains the guide for the needle F, the upper endof the guide C being an excellent ground fit against the lower end ofthe screwthreaded head B. The needle F which has a pointed tip, is boredaxially and has at the centre of its tip a fine injection aperture Kwhich connects the space above the needle F with the combustion chamber.The spring G of the needle F at its upper end, presses a small aperturedplate R on to its seat. The plate R forms an abutment for the smallspring L, which constantly presses on the small throttle valve H. Thestrength of this spring L is so calculated in relation to thecross-section of the seat of the throttle valve H, that when the fuelflows from the delivery pipe into the space above the needle F a certainpressure difference which practically always remains constant is set upbetween the spaces above and below the needle F.

Figure 4 illustrates another construction inwhich the guide p for theneedle F is screwed into the casing A, and the injection nozzleextending from the seat of the needle F has a number of apertures, thatis to say it is of rose form, one of the injection apertures beingdisposed centrally, whilst the others are displaced from the centreposition.

In this embodiment also the fine injection aperture K is arranged in thecentre of the pointed tip of the needle F and the fuel from the apertureK passes through the central aperture of the nozzle rose.

The small throttle valve H is guided in the hollow upper portion of theneedle F, which portion also contains the small spring L.

The seat of the small throttle valve H is situated in the axially-boredcover M screwing into the top end of the guide C.

The operation of. the embodiments of the injector according to theinvention illustrated in Figures 3 and 4 differs from that of theembodiment according to Figure 2 only by reason of the fact that fueldoes not flow into the space above the needle F upon the initiation ofthe pump pressure, but only when the pressure in the delivery pipe hasincreased to such an extent that it is greater than the sum of thepressure of the spring L, of the throttle valve H and the pressure fromthe combustion chamber. As soon as that has occurred, the fuel commencesto flow through the needle F and its injection aperture-K, and when thepump pressure has reached such a value that the difference between thesaid pump pressure and the pressure in the space above the needle Fexceeds the pressure of the loading spring G, the needle F opens.

When the pump pressure terminates, the throttle valve H will closewithin a very short time and the fuel will cease to flow therethrough,possibly before the needle F has definitely closed. If it is desired toutilise a throttle aperture of invariable size, the throttle aperturemay be constituted by a clearance between the needle and its guide, theneedle then not being tightly ground in the guide, but being fitted withan accurately calculated clearance.

The spring G may also be employed to load the throttle valve H, but inthis case the throttle valve must have a diameter of. appropriate size,which is substantially equal to that of the needle.

Furthermore, it is po 'ble to combine the throttling actions by means ofa throttle aperture of invariable size and a spring-loaded throttlevalve, by the provision of a fine throttle aperture below the valve.

with such a construction, the opening of the throttle valve H, andconsequently the commencement of the flow of fuel, occurs as soon as thenecessary pressure difference has been reached. However, thecross-section available for the flow of fuel of the throttle valve H isthen larger than that of the throttle aperture, and the latterdetermines the throttling action.

Obviously, in the construction illustrated in Figure 2 a non-returnvalve may be provided in the delivery pipe merely in order to preventthe combustion gases from being forced back into the delivery pipe.

What I claim as my invention and desire to secure by Letters Patent ofthe United States is:

1. An injection nozzle for internal combustion engines for effecting apreliminary injection of fuel followed by a main injection of fuelduring each fuel injection operation and comprising a casing having anaxially extending guide bore, a first chamber located above said guidebore and in communication therewith, a fuel inlet passage incommunication with said first chamber through a restricted passagehaving a throttling action, a second chamber below said guide bore incommunication therewith and with a fuel outlet opening at the lower endof said casing in communication with the engine cylinder, and a passageleading from said fuel inlet passage to said second chamber; a needleadapted to reciprocate within said guide bore and having a passageextending therethrough leading from said first chamber to said fueloutlet opening through a restricted passage having a throttling action,the lower end of said needle having a surface exposed to the pressure ofthe fuel within said second chamber, which surface terminates in aportion adapted to normally close communication between said secondchamber and said fuel outlet opening, and a spring acting upon the upperend of the needle and tending tohold said needle in its normally closedposition; the arrangement being such that when fuel under pressure is.forced through the inlet passage in the casing a portion of said fuelpasses through the restricted opening leading to the first chamber,through said first chamber, through the passage in the needle, throughthe restricted passage leading from said first chamber to the fueloutlet, through the fuel outlet opening in the casing and into theengine cylinder to constitute the preliminary injection of fuel thereto,and simultaneously with said preliminary injection, fuel is forced underpressure through the passage in the casingleading to said second chamberwhere said pressure acting upon the surface of said needle exposedwithin said second chamher is sufficient to lift said needle from saidfuel outlet opening against the pressure of said spring, whereby themain fuel injection enters the engine cylinder.

2. An injection nozzle as defined in claim 1 wherein the restrictedpassage leading from the fuel inlet passage to the first chambercomprises a fine caliber throttle aperture of invariable size.

3. An injection nozzle as defined in claim 1 wherein the passagethroughthe needle is an axial passage which terminates at its lower endin a restricted passage having a throttling action on the fuel passingfrom the first chamber through the fuel outlet opening in the casing.

4. An injection nozzle as defined in claim 1 wherein the spring whichacts upon the upper end of the needle is disposed in the first chamber.

5. An injection nozzle as defined in claim 1 wherein the pressure of thefuel inthe first chamher assists the spring in normally holding theneedle in closed position with respect to the fuel outlet openingleading from the second chamber into the engine cylinder.

6. An injection nozzle as defined in claim 1 wherein a spring-loadedvalve is interposed in the fuel passage leading from the fuel inletpassage to said first chamber, the loading of the valve cooperating witha substantially conical valve seat formed 'in the casing and surroundingthe fuel outlet opening :from the second chamberto the engine cylinder,said tip normally closing communication between said second chamber andsaid fuel outlet opening, and wherein the restricted passage at thelower end of said needle terminates at the tip thereof and is constantlyin communication with the main fueloutlet opening.

9. An injection nozzle as defined in claim 1 wherein the fuel outletopening leading from the second chamber to the engine cylinder is in theform of a spray nozzle comprising at least two jet.

passages radiating outwardly from a central passage in the nozzle and anadditional jet passage in the nomle disposed in axial alignment with therestricted passage at the lower end of said needle. PROSPER LORANGE.

